The present disclosure relates generally to lighting apparatus and in particular to a zoom lens system for an LED-based spotlight.
The spotlight is a well-known tool in theatrical productions, allowing a bright light to selectively illuminate a portion of the stage (e.g., where an actor is performing) while leaving the rest of the stage less brightly lit. A conventional spotlight includes a light source disposed within a concave (e.g., parabolic) holder, the inner surface of which is coated with reflective material so as to maximize light output. A focusing lens is placed in front of the opening of the concave holder to enhance directionality of the emerging light beam. Some spotlight assemblies allow the focusing lens to be moved along the optical axis to change the beam angle (and the resulting spot size on the stage), providing a “zoom” effect.
Conventional spotlights are made for conventional light sources, such as incandescent or halogen lamps. With the desire for more energy-efficient lighting, there is a demand for spot lights that use more efficient light sources. Light-emitting diodes (LEDs) are an emerging lighting technology. However, whereas conventional lamps tend to illuminate a wide angle, LEDs tend to produce light in a preferred direction (e.g., from the top surface of the diode). Consequently, optical systems such as spotlights that are designed for conventional light sources may not be optimal for use with LED-based light sources.